Process and apparatus for curing tobacco



Aug. 14, 1956 R. R. HELJO 2,758,603

PROCESS AND APPARATUS FOR CURING TOBACCO Filed April 50, 1954 2 Sheets-Sheet 1 INVENTOR. RUNAR R FAEL HsLzro Aug. 14, 1956 R. R. HELJO 2,758,603

PROCESS AND APPARATUS FOR CURING TOBACCO Filed April 30, 1954 2 Sheets-Sheet 2 v In (I u l? E\\\\\ INVENTOR. RUNAR RAFAEL HELTO United States Patent Of PROCESS AND APPARATUS FOR CURING TOBACCO Runar Rafael Heljo, Helsinki, Finland Application April 30, 1954, Serial No. 426,875 Claims priority, application Finland October 24, 1950 3 Claims. (Cl. 131-121) The present invention relates to a new and improved process for curing tobacco and to an apparatus for carrying out said process.

This application is a continuation-in-part of my application Serial No. 227,759 titled Method of Improving the Quality of Tobacco, filed May 22, 1951, now abandoned.

Tobacco leaves contain nitrogenous and other constituents which, when the tobacco is smoked, produce objectionable odors and tastes. These must be removed before the tobacco leaves are incorporated in cigarettes or other smoking tobaccos. Usually, this is accomplished by subjecting the tobacco to biochemical fermentation during which the nitrogenous constituents of the tobacco are decomposed to simpler chemical components and eventually to ammonia and nitrates. The disadvantage of this process is that the curing period is too long, varying from severalmonths to as much as two years. Also, there is the danger during the fermentation process that undesirable bacteria, fungi or the like may contaminate and ruin the tobacco.

It is an object of the present invention to provide a process for curing tobacco which has none of the drawbacks set forth above.

It is a further object of the present invention to provide a new and improved apparatus for curing tobacco in accordance with the new process.

In accordance with the invention, the tobacco is cured by increasing the moisture content thereof to a predetermined amount. The tobacco is then subjected to a high frequency electromagnetic field in order to heat the same to a predetermined temperature during a predetermined interval of time in order .to cause the harmful nitrogenous and other undesirable constituents to become decomposed and to be absorbed by the moisture evaporated from the tobacco. The tobacco is then subjected to the action of a ventilator or similar device in order to withdraw the vapor containing the absorbed undesirable constituents of the tobacco. The resultant product is of high quality, comparable with tobacco which is cured by more conventional methods. The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a longitudinal cross section of an apparatus for curing tobacco in accordance with the present invention; and

Fig. 2 is a cross section along line 22 of Fig. 1.

In the figures, like reference numerals refer to like elements.

Referring now to the drawing there is shown a pair of rollers 10, 11 carrying a pair of endless belts 12, 13

respectively.

2,758,603 Patented Aug. v14, 1 956 Belts 12 and 13 pass over rollers 14 and 15 and into tunnel 36. This tunnel comprises ceramic walls 17 which surround the tunnel and which are supported by housing 16. Pipes 18 carry steam under pressure which passes through apertures 19 in a plate covering an end of pipe 18. Pipes 20 carry heated air which is blown into the space between the ceramic walls 17 and the housing 1 6. High-frequency electromagnetic energy is supplied through lines 25, 26 to electrodes 22, 21 respectively. High voltage electrode 22 is supported by a plurality of stand-01f insulators 23, 24, 35 (Fig. 2) and another insulator not visible in the drawing. Although only :a single pair of high frequency electrodes is shown, it is to be understood that in a preferred embodiment of the apparatus there are two sets or three sets or more of electrodes spaced along the length of tunnel 36 and each set of electrodes has its own high frequency generator. This type of operation is preferable as it permits a more even heating of the tobacco and also it permits the curing process to be continued even if one or more of the high frequency generators should for one reason or another become inoperative. Endless belts 12, 13 continue through tunnel 36 and pass over rollers 30, 31 and28, 29 respectively. A third conveyer belt 32 shown only in part in Fig. 1 moves in the direction of the arrows over pulley 33. Numeral -34 designates a funnel-shaped ventilator hood within which is located a blower motor (no-t shown).

In operation, the uncured tobacco is placed on conveyer belt '13 at the left side of Fig. 1. This tobacco moves in the direction indicated by the arrows, is tightly compressed between the upper and lower conveyer belts 12, 13 and forced into tunnel 36 which is about 10-15 cm. in height. Steam under pressure is forced through aper- 'tures 19 in pipe 18 into the tobacco mass increasing the moisture content of the tobacco to a predetermined desired percentage. The moistened tobacco continues to move along with the endless belts 13, 14 and shortly passes between one or more sets of electrodes 21, 22 which are supplied with high frequency electromagnetic energy at a frequency of from 16-60 megacycles. The tobacco is heated very rapidly by the high frequency electromagnetic field and the temperature can be regulated very closely. Using high frequency generators of sufficient capacity, it has been found possible to raise the temperature of l kilogram of tobacco from room temperature to C. within a minute or less. The temperature of the tobacco can be controlled Within 0.5%. The hot air blown into the cavity through pipes 20 between walls 17 and housing 16 maintain the tunnel at the proper operating temperature during the curing process.

The high frequency heating .of the tobacco apparently causes the nitrogenous and other undesirable tobacco constituents to be decomposed and the liquid inside of the tobacco cells to be evaporated and to absorb these constituents. The same thing happens to the nicotine in the tobacco to some extent.

After the heating process is completed, the tobacco is carried by endless belts 12, 13 to the right side of the apparatus shownin Fig. i and the tobacco then drops on "to moving endlessbelt .32. It then passes beneath ventilator 34 which draws up the vapor created during the high frequency heating and with it the absorbed undesirable tobacco constituents.

Although shown here as a funnel-shaped ventilating device, it is to be understood that there are other means which are equally applicable for the removal of vapor. For example, the tobacco may be deposited in a rotating drum through which air is blown or evacuated.

In order better to understand the invention, several examples will be given of the process of curing tobacco 1n accordance with the invention:

Example I In the general case, the tobacco is first treated with steam until the moisture content of the tobacco is raised to about 18-25% and then subjected to a high frequency electromagnetic field for a period of from 1-3 minutes during which period the temperature of the tobacco is rapidly increased to and then maintained at 80-120 C. The dielectric heating of the tobacco causes a portion of the moisture content thereof to vaporize and absorb the nitrogenous and other harmful constituents of tobacco. This vapor is then drawn 01f by passing the tobacco under a ventilator.

As is well known, in making cigarettes of the American type, a certain amount of Burley tobacco is employed in the tobacco blend. It is usually curved by the so-called dipping method in which the tobacco is first dipped in a solution in which it remains for a predetermined interval of time and then forced through rollers to reduce the moisture content thereof to 55%. It is then dried at a temperature of 140 C. until it is hard and then the moisture content of the tobacco is again increased until its final moisture content is 16%. After the Burley tobacco is cured, it is mixed with flue-cured and Oriental tobaccos in the desired proportions and cut to the desired size. The dipping method of curing Burley tobacco is both difficult and very expensive.

In accordance with the present invention, uncured Burley tobacco can be processed into cigarette blends without using the dipping method. The treating process is as follows:

Example 11 Flue-cured and raw Burley and Oriental tobaccos are cut up into strips and mixed with each other in the proportions desired. In usual cigarette blends, the Burley content is about 33-35%. A curing liquid containing sugar and hygroscopic compounds is then sprayed into the mixture and the mixture is allowed to stand for about a day. The mixture is then cut up and driven through the high-frequency tunnel illustrated in Figs. 1 and 2. As already mentioned, if the moisture content of the tobacco is lower than about 18-25% steam is added under pressure to the tobacco mass by means of steam pipe 18 until the moisture content is proper. The tobacco is then heated to 100-105 C. for about 2 minutes. After the completion of the high frequency heating, the vapor and its absorbed substances is removed and the tobacco is allowed to stand at room temperature for about 24 hours. It is then flavored and is ready to be made into cigarettes.

Although very good results have been obtained with the process described above, in a preferred embodiment of the invention the Burley tobacco is cured separately prior to the blending of the tobaccos. This is because Burley tobaccos require higher curing temperatures than the flue-cured and Oriental types of tobacco. Separate curing of the Burley tobacco is accomplished as follows:

Example III The Burley tobacco is cut into strips and subjected to steam until the tobacco attains a moisture content of about 12%. The moistened tobacco is then sprayed with a sufficient amount of 4-4 /2% cane sugar in water solution to raise the moisture content of the tobacco to 17%. The sprayed tobacco is allowed to stand for 24 hours at a temperature of 24 C. and a relative humidity of about 70-75%. It is then passed through the high frequency tunnel shown in the drawing. During the high frequency treating process, the temperature of the compressed tobacco is raised to 100-105" C. in a period of about 1 minute. After the completion of the heating of the tobacco, the vapor produced and its absorbed substances is removed by the means already described. The vapor removed from the tobacco is so noxious that people who inhale it become quite ill. The tobacco is allowed to stand for about 24 hours at room temperature and it is then mixed with the other tobacco components, cut to size, flavored and made into cigarettes. During the high frequency heating process, and subsequent removal of vapor, the moisture content of the tobacco is reduced to about 3-4%.

Example IV The midribs are first sprayed with a curing sauce and allowed to stand at a temperature of from 3535 C. and at a relative humidity of about until they are soft. The soft midribs are then compressed into a sheet 0.5 millimeter thick and cut into strips strips per inch). When processed in this manner prior to being subjected to high frequency heat, the tobacco does not perforate the cigarette paper during the manufacturing of the cigarettes and also the tobacco does not have too ojectionable a flavor.

After the steps described above, the cut up midribs are moistened and forced through the high frequency tunnel, heated to a temperature of about l00-110 C. for about 1-3 minutes, and then any excess of moisture is evaporated as in the manner already described. The curing destroys the woody taste which the midribs would otherwise impart to the cigarette. It is therefore possible to use a substantial amount of this constituent in the final cigarette blend and thereby considerably re duce the price of the product. It should be noted that about 20% by weight of flue-cured tobacco comprises midribs.

The importance of the use of Burley tobacco cured in accordance with the process described here in the manufacture of cigarettes must be stressed. As is well known, in American type cigarettes a certain amount of Burley tobacco must be used. Higher quality Burley tobaccos which are used in the better blends come from the base and middle portions of the tobacco plant. In accordance with the present invention, it has been found possible also to utilize the cheaper grades of Burley tobaccos which come from the top portions of the plant, commonly known as tips or leaf, without adversely affecting the quality of the blend. These cheaper Burley grades cost only one-half or so as much as the more expensive Burley tobaccos. In some cigarette tobacco blends solely cheaper grades of Burley are used as the Burley component. In other cigarette blends, the Burley component comprises part cheaper grade Burley and the rest regular grade Burley. In both cases, a considerable saving of money results.

Using the present process, it has been also found possible to use cheaper grades of flue-curd tobacco without hamfully effecting the quality of the cigarette blend. And even further reduction in cost is made possible when tobacco midribs cured in accordance with the present process are used in the blend.

In tobacco cured in accordance with the process described herein, as already mentioned, the content of nitrogenous compounds is reduced considerably. Also, the carbohydrate content, as measured by Fehling solution tests, increases, and the ash content decreases. In general, the chemical properties of the tobacco are enhanced.

Analysis of tobacco cured in accordance with the present invention, indicates that the tobacco become more acid, as indicated by pH determinations. This means that some of the substances in the tobacco tending to make the tobacco basic are eliminated during the process.

The taste of the tobacco cured in accordance with the present invention also is much improved.

The physical properties of the tobacco when cured in accordance with the present method are also considerably improved. For example, the lemon-colored flue-cured type changes noticeably in the red direction. Even G- class flue-cured tobacco is changed in this respect. The

same tendency is apparent in other types of tobaccos such as Burley, for example. The explanation of this phenomenon may be that the waxes in the tobacco when heated are drawn to the surface of the tobacco leaf.

The internal cell pressure which is produced during the high-frequency heating process causes the tobacco to become more porous. The tobacco also becomes very loose and easy to burn and the burning temperature of the to bacco, when drawing smoke through the cigarette, rises. Smoke is generated much more quickly and the tobacco aroma is more pronounced. The tobacco burns more completely than the conventional tobaccos because of its porosity, and because of the more complete burning of the tobacco, there is less carbon monoxide generated.

The increased porosity of the tobacco also causes the volume of the tobacco to be increased by about 5-10%. This is important because it permits less tobacco to be used per cigarette and accordingly there is less cost per cigarette.

While the invention has been illustrated and described as embodied in a process and apparatus for curing various specific types of tobacco, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A process for treating Burley tobacco comprising the steps of cutting raw Burley tobacco into strips; applying moisture to the strips of tobacco until the moisture content thereof is about 12%; spraying the moistened tobacco with a curing liquid comprising a 4-4V2 solution of cane sugar in water so as to increase the moisture content thereof to about 17%; allowing the sprayed tobacco to stand for about a day at room temperature and at a relative humidity of about 70-75%; placing the sprayed tobacco in a high frequency electromagnetic field so as to heat the same to a temperature of about 100-10S C. for a period of about 1-3 minutes, thereby causing a portion of the liquid in said tobacco to be vaporized and nitrogenous and other undesirable constituents of the tobacco to be absorbed by said vaporized liquid; and removing from said tobacco said vaporized liquid and the tobacco constituents absorbed by said vaporized liquid.

2. A process for treating Burley tobacco comprising the steps of cutting raw Burley tobacco into strips; applying moisture to the strips of tobacco until the moisture content thereof is about 12%; spraying the moistened tobacco with a curing liquid comprising a 44 /2% soution of cane sugar in water so as to increase the moisture content thereof to about 17%; allowing the sprayed tobacco to stand for about a day at room temperature and at a relative humidity of about -75%; placing the sprayed tobacco in a high frequency electromagnetic field so as to heat the same to a temperature of about 105 C. for a period of about l-3 minutes, thereby causing a portion of the liquid in said tobacco to be vaporized and nitrogenous and other undesirable constituents of the tobacco to be absorbed by said vaporized liquid; removing from said tobacco said vaporized liquid and the tobacco constituents absorbed by said vaporized liquid; allowing the tobacco from which the vaporized liquid has been removed to stand for about 24 hours at room temperature; and blending the tobacco with other types of tobacco to form a tobacco blend.

3. A process for treating Burley tobacco comprising the steps of cutting raw Burley tobacco into strips; applying moisture to the strips of tobacco until the moisture content thereof is about 12%; spraying the moistened tobacco with a curing liquid comprising a 4-4V2% solution of cane sugar in water so as to increase the moisture content thereof to about 17%; allowing the sprayed tobacco to stand for about a day at room temperature and at a relative humidity of about 70-75%; placing the sprayed tobacco in a high frequency electromagnetic field so as to heat the same to a temperature of about 100-105 C. for a period of about 1-3 minutes, thereby causing a portion of the liquid in said tobacco to be vaporized and nitrogenous and other undesirable constituents of the tobacco to be absorbed by said vaporized liquid; removing from said tobacco said vaporized liquid and the tobacco constituents absorbed by said vaporized liquid until the moisture content of the tobacco is reduced to about 3-4%; and allowing the tobacco to stand for about 24 hours at room temperature.

References'Cited in the file of this patent UNITED STATES PATENTS 3,673 Huse July 22, 1884 240,252 Huck Apr. 19, 1881 1,219,856 Parker Mar. 20, 1917 1,589,480 Nagel June 22, 1926 1,813,833 Andrews July 7, 1931 2,124,012 Smith July 19, 1938 2,498,632 Anderson et al Feb. 28, 1950 2,500,752 Hanson et a1. Mar. 14, 1950 2,512,311 Davis June 20, 1950 FOREIGN PATENTS 361,301 Great Britain May 13, 1930 499,764 Great Britain Jan. 27, 1939 608,430 Germany Mar. 20, 1930 699,725 Great Britain Nov. 11, 1953 706,052 Great Britain Mar. 24, 1954 OTHER REFERENCES Drying and Processing of Materials, page 181; published 1929 by Carrier Engineering Corp., Newark, N. 1.

Ser. No. 304,214, Bohme et al. (A. P. C.) published May 11, 1943. 

